United States
                Environmental Protection
 Risk Reduction
 Engineering Laboratory
 Cincinnati, OH 45268
                Research and Development
 EPA/600/SR-94/063    May 1994
EPA        Project  Suimmary
                Wash  Solvent  Reuse  in  Paint
                Alice B. Parsons, Kenneth J. Heater, and Robert F. Olfenbuttel
                  This project evaluated solvent used
                to clean paint manufacture equipment
                for its utility in production of subse-
                quent batches of  solvent-borne paint.
                Reusing wash solvent would reduce
                the amount of solvent disposed of as
                waste. The evaluation of this wash-sol-
                vent  recovery technology was con-
                ducted  by Battelle Memorial  Institute
                for the  Pollution Prevention Research
                Branch  of the U.S. Environmental Pro-
                tection  Agency. The evaluation was
                conducted with the cooperation and
                assistance of Vanex Color, Inc.
                  The product quality, waste reduction/
                pollution prevention, and economic im-
                pacts of this technology change, as it
                has been implemented by Vanex, were
                examined. Two batches of a  solvent-
                borne alkyd house paint were prepared
                at Vanex—one batch made with 100%-
                new solvent and the  other with 80%-
                wash  solvent—and   sampled  for
                laboratory analysis at Battelle. Product
                quality was evaluated  by Battelle ac-
                cording to appropriate ASTM Itest meth-
                ods  and  by Vanex  quality-control
                personnel according to normal produc-
                tion procedures. Waste reduction and
                economics were  documented from
                company records  and  interviews with
                key company personnel. The technol-
                ogy was found to reduce waste and
                operating costs without affecting prod-
                uct quality.
                  This Project Summary was developed
                by the EPA's Risk Reduction Engineer-
                ing Laboratory, Cincinnati, OH, to an-
                nounce  key findings  of the research
                project  that is fully documented in  a
 separate report of the same title (see
 Project Report ordering information at

  The Pollution Prevention  Research
 Branch (PPRB) of the U.S. Environmental
 Protection Agency is evaluating and dem-
 onstrating pollution  prevention technolo-
 gies through the Pollution Prevention Clean
 Technology Demonstration (CTD) Pro-
 gram. The CTD program focuses on tech-
 nologies  that can be used within a
 particular industry to minimize the source
 of pollution  problems.  This study, con-
 ducted by Battelle,  evaluated a technol-
 ogy for reducing solvent waste by reusing
 wash solvent in the  manufacture of paint.
 The solvent used to clean equipment at
 the  end of a production run is stored for
 use in the next formulation  of the same
 type of paint.
  Three aspects of  this technology were
 evaluated: product quality, pollution pre-
 vention, and economics. The goal of this
 solvent reuse study was to evaluate (1)
 the  quality of the paint formulated with
 wash solvent to ensure that product qual-
 ity has not been compromised, (2) the
 amount of solvent diverted  from the
 wastestream by this technology, and (3)
 the cost to operate this pollution preven-
tion program.
  The site selected  for  evaluation of this
technology was Vanex Color, Inc., located
 in Mt.  Vernon,  IL. Small amounts of sol-
 vent are used  to clean the batch tanks
 and the dispensing equipment. Vanex
stores mineral spirits used to clean mixing
and dispensing equipment after produc-
                                                                  Printed on Recycled Paper

tion of each batch of paint and reuses this
wash solvent as part or all of the solvent
needed  to manufacture subsequent
batches of solvent-borne paint. The per-
centage  of reused solvent varies from
batch to batch and depends on the amount
of stored solvent available at the time of
  Only certain coatings are formulated with
the stored wash solvents. Product lines
selected by Vanex for  its solvent reuse
program were primarily those that could
be easily formulated  to  meet final color
requirements.  The  Vanex technical staff
put together a master  list of wash sol-
vents and paints that could be formulated
with the wash  solvents, based on the
chemistry of the polymers, the color of the
pigments, and  the  gloss  required in the
paint being mixed. Wash solvents (min-
eral  spirits) stored for reuse are  assigned
to storage drums in one of three solvent
recovery groups.
  Solvent is stored in labeled 55-gal drums
for addition back into the same or very
similar paint formulations within  90 days.
During the first 24 hr of storage, pigment
settles out of the wash  solvent and col-
lects at the bottom of the drum.  There-
fore, when solvent is removed  from the
drum to be added to a production batch,
care Is taken to ensure that none of the
sediment (mostly pigments) in the bottom
of the drum is added to the formulation.
Solvents  not selected for reuse are col-
lected In drums and shipped to,a solvent
blender who processes and sells the mixed
solvent to a cement kiln as a fuel additive.
                 Results and Discussions

                 Product Quality Evaluation
                   The paint formulated with wash solvent
                 should meet the same product specifica-
                 tions  established by Vanex for paint for-
                 mulated with  100%-new solvent. For this
                 study, two batches of a solvent-borne alkyd
                 house paint were prepared at Vanex, un-
                 der the observation of the Battelle Labo-
                 ratory Manager conducting this study. One
                 batch was formulated with 100%-new sol-
                 vent  and  the  other with 80%-wash  sol-
                 vent.  Vanex personnel ran their standard
                 quality-control tests on each batch,  and
                 field samples  were collected by  Battelle
                 for further laboratory analysis. The same
                 series of standard analytical tests was run
                 on each batch.
                    Vanex  quality  assurance personnel
                 evaluated samples in  the field after the
                 initial formulation and  after a 16- to 24-hr
                 holding period. The paint formulated  with
                 80%-wash solvent  compared well with the
                 paint formulated with  100%-new  solvent.
                 Table 1 shows the Vanex quality-control
                 test results for both batches of coatings.
                 The  paint made with wash  solvent re-
                 quired no adjustments to meet  the ex-
                 pected ranges. The paint formulated with
                 100%-new solvent required the  addition
                 of 2 gal of mineral spirits to bring the final
                 viscosity from 91 Krebs units to 89 units.
                    Vanex rated these two batches of alkyd
                 house paint as comparable in quality be-
                 cause quality-control  data  for  the two
                 batches  indicated  a close match for the
                 tested parameters. The company's qual-
ity-control procedures use a visual match
of wet color. The color of a coating batch
being mixed is checked against a stored
color standard by visual  comparison of
wet side-by-side drawdowns of the batch
and  the appropriate  color standard. The
Vanex quality-control staff judged the wet
color of both of the batches prepared and
sampled for this study to match the color
standard without adjustment.
  Further laboratory analysis at Battelle
of the field samples collected during the
site  visit supported this conclusion. The
tests used at Battelle and the test results
are  listed in  Table 2. The gloss of the
wash-solvent batch tested slightly higher
than that of the new-solvent batch, but not
statistically different. The average percent
solids for the coating batch manufactured
with new solvent was 26.6%; the percent
volatiles, 73.4%. The average percent sol-
ids for the batch manufactured with wash
solvent was 26.5%; the percent volatiles,
73.5%.  The results of the percent solids/
percent volatiles determination show that
the use of wash solvent did not affect the
solids and volatiles  content of the paint
formulated.  The  viscosity determination
also revealed no difference between the
batch manufactured with wash solvent and
the one formulated with new solvent. The
instrumental measurement of dry film color
as color difference (AE) calculated  by the
CIELAB formula  indicated no significant
difference in color between the batch made
with  100%-new  solvent  and  the  batch
made with 80%-wash solvent.
 Tablo 1, Results of Quality-Control Tests for Product Quality Assessment Performed at Vanex

 Property (Units)                  Test Method'               Vanex Range*           New-Solvent Batch
                                                                             Wash-Solvent Batch
 Viscosity (Krebs Units)

 Density (Jo/gal)

 Grind (Hegman Scale)
 Unear flow (sag)


 Gloss (gloss units)
ASTM D562-81 (reapproved 1990)         88±2

ASTM D1475-90                     10.36±0.05
                                   (1.24± 0.0)

ASTM D1210-79                        >5
(reapproved 1988)

ASTM D4400-89a                       12

Visual comparison with               Match stored
stored standard                       standard

ASTMDS23-89 (60°)                   >80








 ' American Society for Testing and Materials, 1992 Annual Book of ASTM Standards, Vol. 06.01, "Paint -
  Tests for Formulated Products and Applied Coatings."
 t Approved range for Vanex #2-1 alkyd housepaint.

 Table 2. Results of Tests for Product Quality Assessment Performed at Battelle
Property (Units)
Viscosity (Cent/poises)
Density (Ib/gal)
Grind (Hegman Scale)
Percent Solids (%)
Percent Volatiles (%)
Color (A E) CIELAB
Gloss (gloss units)
Test Method*
(reapproved 1991)
ASTMD1 475-90
(reapproved 1988)
New-Solvent batch
data not valid
Standard for Comparison
Wash-Solvent Batch
data not valid
"American Society for Testing and Materials, 1992 Annual Book of ASTM Standards, Vol. 06.01,
 "Paint —Tests for Formulated Products and Applied Coatings."
                                             Employees at Vanex make a conscious
                                           effort to minimize the amount of solvent
                                           required for cleaning by techniques such
                                           as physical scraping of the  mix tanks to
                                           remove many paint solids before solvent
                                           cleaning. Workers minimize  the  need for
                                           cleanup of work areas and equipment by
                                           taking care when  adding raw  materials
                                           and dispensing finished batches. They ar-
                                           range production schedules so that, when-
                                           ever possible, similar batches of paint are
                                           mixed and dispensed one after another to
                                           eliminate cleanup between batches.
                                             The volume of wash solvent diverted
                                           from the wastestream could vary from year
                                           to  year, depending on  the  product  mix
                                           and the annual production. This  low-tech
                                           system has,  however,  produced an  ap-
                                           preciable reduction  in  solvent  waste at
                                           Vanex. Production figures and background
                                           information collected during two site visits
                                           to Vanex (Table 3) indicate that, in 1992,
                                           Vanex diverted  about 3,300 gal (12,500
  The sample size was limited to  two
batches  of  paint,  but the quality-control
tests at Vanex and the laboratory analysis
at Battelle indicate that the quality of the
solvent-borne alkyd house paint made with
wash solvent  is comparable with that of
the product quality of the same paint made
with 100%-new  solvent. These results
compare  well with  the experience that
Vanex has  accumulated during the sev-
eral years it has used this wash-solvent
recovery system.

Pollution Prevention Potential
  Waste  is  reduced in two  ways  when
this technology is practiced as at Vanex
for  manufacture of solvent-borne paints:
(1)  disposal of wash solvent is reduced
and (2) solvent purchase for paint manu-
facture is reduced. In addition, the use of
this technology did not increase other types
of pollution.                        '•   '
  Solvent required to  clean the  mixing
and dispensing  equipment  .between
batches  is the major source of solvent
waste in the manufacture of solvent-borne
paint. Information from company records
and from interviews  with key  staff was
gathered to determine the volume of wash
solvent (mineral spirits) diverted from the
wastestream by implementation of the re-
use program at Vanex.
Table 3. Annual Waste Reduction Through Wash-Solvent Reuse Program at Vanex Color, Inc.
Vanex Production Data:

Production in 1992 of solvent-borne paints:

 Average batch size

  Estimated number of batches/year:

  Quantity of mineral spirits used to clean
  tanks and equipment between batches:

Wash Solvent Calculations:

Without Reuse

  Solvent required for cleanup only
  (206 batches X20 gal/batch)

  Wash solvent disposed

With Reuse

  Solvent required for cleaning only
  (206 batches X 20 gal/batch)

  Solvent reused for formulation
  (80% X 4,120 gal)

  Wash solvent disposed

Waste Reduction
82,500 gal (312,000 L)

  400 gal (1,500 L)

    206 batches

    20 gal (75 L)
 4,120 gal (15,600 L)

 4,120 gal (15,600 L)

 4,120 gal (15,600 L)

 3,300 gal (12,500 L)

  820 gal (3,100 L)

 3,300 gal (12,500 L)

ume of solvent waste requiring disposal
from 13.6 million gal to 2.7 million gal, a
reduction of 10.9 million gal.

Economic Evaluation
  The objective of the economic estima-
tion was to calculate a  payback period
and/or  cost reduction associated  with
implementation of this technology for  re-
ducing  the solvent wastestream. Imple-
mentation of  the  wash-solvent reuse
system at Vanex did not  have significant
capital  costs.  No   equipment was  pur-
chased, no additional storage area was
needed, and no additional energy- or air-
supply systems were required. Vanex per-
sonnel  estimate the total cost (materials
and labor) of establishing the solvent-re-
use system at less than $1,000.
  Because the reuse program has reduced
substantially the quantities of solvent that
must  be  purchased and  disposed  of,
Vanex  estimates that it  saves  $15,000
annually in raw material purchases and
disposal costs. For this economic evalua-
tion, Battelle used a conservative estimate
of $11,600 for 1992 savings. Other oper-
ating  costs have not been affected. Labor
costs for  handling wash  solvent are the
same whether the solvent is disposed of
or stored  for reuse, and drums to collect
         Estimate of Annual Waste Reduction if Wash Solvent Reuse Implemented
 Throughout the U.S.
L) of mineral spirits (60 drums/year) from
the wastestream to product formulation.
This represented an 80% reduction In min-
eral spirits disposed of as waste that year.
  Interim storage of wash solvent for re-
use at Vanex does not create an addi-
tional source of pollution. Wash solvent is
stored in closed barrels  in the  same way
that waste solvent  is stored to await dis-
posal. The maximum  storage  on-site for
any waste is 90 days. At Vanex, produc-
tion batches are planned such that stored
solvent is used in less than 90  days.
  Using the Vanex solvent recovery rate
and  U.S. production figures for solvent-
boms coatings, ft is possible to estimate
the effect that adoption of this technology
could have on wash-solvent waste reduc-
tion each year in the U.S. (Table 4). Ac-
cording to U.S. Department of Commerce
figures, production  of paints in the U.S. in
1992 was 1.10 billion gal. Industry figures
suggest  that about 62% of this volume
(682 million gal) was solvent-borne coat-
ings in 1992, although the percentage has
been falling each year.
   Equipment cleaning in production of 682
million gal of solvent-borne paint cbuld
generate as much as 13.6 million gal "of
waste wash solvent. Recovery of 80% of
this  wash solvent  could reduce the vol-
Assumptions Based on Industry Data:

  Annual production of solvent-borne paints:

  Estimated number of batches @ 1,000 gal/batch:

  Quantit/ of mineral spirits used to clean
  tanks and equipment between batches:

 Wash Solvent Reduction Calculations:
                 682 million gal
                 (2,580 million L)
                 682,000 batches

                 20 gal/batch
                 (75 L)
Without Rouse
Solvent required for cleanup only
(682,000 batches X 20 gal/batch)
Wash solvent disposed
With 80% Reuse
Solvent required for cleanup
(682,000 batches X 20 gal/batch)
Solvent reused for formulation
(80% X 13.6 million gal)
Wash solvent disposed
(13.6 -10.9 million gal)
Waste Reduction
13.6 million gal
(51. 5 million L)
13.6 million gal
(51. 5 million L)
13.6 million gal
(51. 5 million L)
10.9 million gal
(41. 3 million L)
2.7 million gal
(10.2 million L)
10.9 million gal
(41. 3 million L)
the solvent are  required in  either case.
Labor costs for  adding the stored wash
solvent to the paint formulation do not add
significant cost to the mixing operation.
  Using the cost of implementation and
the savings resulting from decreased waste
of solvent, the payback  period for  imple-
mentation of the wash-solvent recovery
system at Vanex was found to have been
approximately one month.

  Payback = $1.000

  Payback ~ one month

  Savings for other companies instituting
similar systems will vary with production
volumes and the volume of wash solvent
recovered from the wastestream.

Conclusions and
  The major source of  solvent waste in
paint manufacture is wash solvent used to
clean tanks and equipment. The very sim-
plicity of this technology makes it desir-
able for paint companies actively pursuing
reduction of solvent waste. It is especially
useful for small-to-medium  companies
manufacturing several solvent-borne paints
in small production batches.
  The quality-control tesrts at Vanex and
the  laboratory analyses at Battelle indi-
cate that the product quality of a batch of
solvent-borne alkyd  house paint made with
a formulation in which 80% of the solvent
had been recovered from equipment-clean-
ing operations was comparable to that of
a batch made with  100%-new solvent. All
Vanex products must meet specific qual-
ity-control standards. The experience that
Vanex has accumulated while using this
wash-solvent recovery system for several
years  is that paint formulated with se-
lected wash solvent meets its  quality as-
surance  standards  and  those  of  its
   Reusing wash solvent in the subsequent
formulation of coating products (1) reduces
the  amount of wash solvent that must be
disposed of as waste and (2) reduces the
amount of solvent that must be purchased
for use in paint formulations. Interim stor-
age of the wash solvent before reuse does
not contribute to additional pollution. Vanex
is able to  reuse about 3,300 gal of min-
eral-spirits wash solvent per year.
   The payback  period for implementation
of the wash-solvent  recovery system  at
Vanex was about one month. Vanex has
estimated yearly savings through the wash
solvent recovery  system  at $15,000;
 Battelle's conservative estimate of yearly

savings was $11,600 per year based on
Vanex's figures for 1992. Capital costs in
the first year were estimated at less than
  The results  of this evaluation  suggest
that the wash-solvent recovery system can
be used by manufacturers of solvent-borne
paint to reduce the volume of solvent waste
without affecting product quality, as well
as positively  impacting the environment.
Sound experience and knowledge of the
chemistry of the paint formulations is
needed to plan a reuse protocol  for a
particular facility. This technology system
can produce cost savings with little capital
outlay for  implementation and little  or no
increase in operating  expenses.
  The U.S. EPA and Battelle  acknowl-
edge the cooperation  and support of the
technical and administrative staff of Vanex
Color, Inc., during the  technology evalua-
tion  process.  Ken Brandt  and Walter
Rexing provided technical information and
assistance with production scheduling that
made the program possible.
                                                                    *U.S. GOVERNMENT HUNTING OFFICE; I»M - S5


Alice B. Parsons, Kenneth J. Heater, and Robert F. Olfenbuttel are with
  Battelle, Columbus, OH 43201.
Lisa Brown is the EPA Project Officer (see below).
The complete report, entitled'Wash Solvent Reuse in Paint Production," (Order
    No. PB94-161130; Cosl;$17.50, subject to change) will be available only
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
        Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
        Risk Reduction Engineering Laboratory
        U.S. Environmental Protection Agency
        Cincinnati, OH 45268
   United States
   Environmental Protection Agency
   Center for Environmental Research Information
   Cincinnati, OH 45268

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